1. Field of the Invention
The present invention relates to a control method of a motor driving apparatus using a DC/DC converter and an inverter.
2. Description of Related Art
As an example of a conventional motor driving apparatus used for an electric vehicle or HEV (Hybrid Electric Vehicle), a motor driving apparatus disclosed in Relevant Reference 1 is known. The motor driving apparatus includes a motor, an inverter for converting DC power to AC power, a high voltage battery, a DC/DC converter and a DC link capacitor. The DC/DC converter boosts the voltage fed from a high voltage battery and supplies the DC power to the inverter during power running, and decreases the voltage of the DC power output from the inverter and supplies it to the high voltage battery during regenerative running. The DC link capacitor, which includes a plurality of capacitors, is interposed between the DC/DC converter and the inverter to smooth the DC voltage.
Relevant Reference 1: Japanese patent application laid-open No. 8-214592/1996.
The conventional motor driving apparatus has the following problems. First, a power conversion unit constructed by integrating the inverter, DC/DC converter and DC link capacitor into a module to downsize the unit has a problem of increasing the ripple current flowing through the DC link capacitor because of interaction between the current pulses fed from the DC/DC converter to the DC link capacitor and the current pulses fed from the DC link capacitor to the inverter. Second, a configuration that limits the ripple current per capacitor within a tolerance to maintain the life of the DC link capacitor has a problem of increasing the size of the DC link capacitor, which in turn increases the size of the unit in its entirety.